1 / 7

Confusion and Diffusion

Confusion and Diffusion. Ref: William Stallings, Cryptography and Network Security, 3rd Edition, Prentice Hall, 2003. Statistics and Plaintext. Suppose the frequency distribution of plaintext in a human-readable message in some language is known.

Download Presentation

Confusion and Diffusion

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Confusion and Diffusion Ref: William Stallings, Cryptography and Network Security, 3rd Edition, Prentice Hall, 2003 Confusion and Diffusion

  2. Statistics and Plaintext • Suppose the frequency distribution of plaintext in a human-readable message in some language is known. • Or suppose there are known words or phrases that are used in the plaintext message. • A cryptanalysist can use this information to break a cryptographic algorithm. Confusion and Diffusion

  3. Changing Statistics • Claude Shannon suggested that to complicate statistical attacks, the cryptographer could dissipate the statistical structure of the plaintext in the long range statistics of the ciphertext. • Shannon called this process diffusion. Confusion and Diffusion

  4. Changing Statistics (p.2) • Diffusion can be accomplished by having many plaintext characters affect each ciphertext character. • An example of diffusion is the encryption of a message M=m1,m2,... using a an averaging: yn= i=1,k mn+i(mod26). Confusion and Diffusion

  5. Changing Statistics (p.3) • In binary block ciphers, such as the Data Encryption Standard (DES), diffusion can be accomplished using permutations on data, and then applying a function to the permutation to produce ciphertext. Confusion and Diffusion

  6. Complex Use of a Key • Diffusion complicates the statistics of the ciphertext, and makes it difficult to discover the key of the encryption process. • The process of confusion, makes the use of the key so complex, that even when an attacker knows the statistics, it is still difficult to deduce the key. Confusion and Diffusion

  7. Complex Use of a Key(p.2) • Confusion can be accomplished by using a complex substitution algorithm. • Block ciphers, such as the Data Encryption Standard, makes use of substitution operations. Confusion and Diffusion

More Related